1. Field of the Invention
The present invention relates generally to a disk drive unit and disk drive method, and more particularly, to a disk drive unit and disk drive method for reproducing information recorded on a disk-like recording medium such as a digital versatile disk (DVD).
2. Description of the Related Art
A variety of DVDs exist, from the DVD-Video targeted for popular use in audio-visual entertainment to the DVD-R, DVD-ROM and DVD-RAM used for commercial and other data storage purposes.
The DVD-ROM drive units that read DVD-ROMs typically are able to read both DVD-Video and DVD-ROM. More recently, this type of DVD-ROM drive unit has seen advances in playback speed intended to increase the data transfer rate, until at present such devices have playback speeds up to 8 times faster than the standard speed at which DVD-Video disks are normally played.
With the conventional DVD-ROM drive unit, the loaded disk is read at maximum speed when a read command is received from an upstream device, without regard to whether the loaded disk is a DVD-ROM or a DVD-Video disk.
Such rapid read speeds pose no problem if the loaded disk is a DVD-ROM. However, if the loaded disk happens to be a DVD-Video disk, it can happen that the speed with which data is read from the disk takes place at a transfer rate exceeding that which is required by the upstream device for video and audio data reproduction, resulting in a needless increase in the consumption of electric current needed to rotate the disk.
Additionally, in general the playback time needed for DVD-Video disks is typically longer than that required for DVD-ROM, resulting in additional power consumption. If the above-described DVD-ROM drive unit is one that is installed in a laptop-type personal computer, excessive power consumption becomes a major disadvantage.
Additionally, high data transfer rates mean high disk rotation speeds, resulting in unacceptably heavy vibrations for the unit itself.